Why do human have five fingers but not less? Are ring and little fingers useful?
This was selected as Best Answer All animals actually have 7 fingers, 2 being lost during embryogenesis. The number of fingers is driven by morphogenetic gradients that, roughly speaking, force each bone to attach to 2 bones starting from your shoulder (or from your hip for that matter). Therefore you have one humerus connected to the radius and the ulna, which in turn connect to the 3 proximal carpals in your wrist, which in turn connect to 5 distal carpals and finally to 5 metacarpals (remember that 2 are lost during embryogenesis). This goes the same for legs. This is true for all mammals, although some adaptations may have occurred that somewhat change the final structure. For example, although all these bones are present in horses, the metacarpals are fused to lead to a structure strong enough to support the hoof. Therefore they appear to have only one finger. On the contrary, whales have both polydactily and polyphalangy (more than 3 phalanges and more than 5 fingers) as a result
